Apparatus and method for supplying a heated liquid

ABSTRACT

An improved method and apparatus for effecting delivery of a chemical solution useful in the softening of tooth caries and/or plaque in a patient&#39;s mouth utilizes a reciprocating piston-type pump having flow and pressure regulation for injecting a pulsating jet stream of the solution at a controlled rate and pressure, in combination with a separate heater device adjacent an applicator maintaining the temperature of the solution at or near body temperature as it is delivered to the mouth.

BACKGROUND OF THE INVENTION

This invention relates to an apparatus for supplying a liquid heated toa predetermined temperature. In particular, the invention relates to anapparatus for intermittently supplying a dental treating solution to theoral cavity of a patient with the solution being heated to about thenormal body temperature of the patient, and to a method of treatingemploying such apparatus.

A common method for removing carious lesions in teeth is through the useof power operated tools in conjunction with hand manipulated tools.Thus, complete removal of carious material by the dentist requires theuse of rotary cutting instruments as well as hand instruments. Suchdental procedures impart a high degree of apprehension and fear to manydental patients, particularly children. Other dental patients haveproblems and/or reactions with local anesthetic injection which areoftentimes given in those instances where the carious lesions are fairlyextensive and deep.

Within the past decade, methods have been developed which utilizecertain chemical solutions to soften and remove dental caries. Suchmethods substantially reduce and even eliminate the need for mechanicalremoval of the carious lesion by the use of drills and burrs. Suitablesolutions can be prepared by forming an admixture containing (a) atleast one aminoalkanoic acid containing from 1 to about 18 carbon atoms,e.g., DL-2-aminobutryic acid, glycine, etc., (b) an alkali metalhydroxide, e.g., sodium hydroxide, (c) an alkali metal halide, e.g.,sodium chloride, and (d) an alkali metal hypochlorite, e.g., sodiumhypochlorite, in deionized water and preferably maintained at a pH offrom about 9 to about 12. The active ingredient is believed to beN-chlorinated aminoalkanoic acid(s) and/or the alkali metal salt(s)thereof. A preferred formulation is (a) DL-2-aminobutyric acid and/orglycine, (b) sodium hydroxide, (c) sodium chloride and (d) sodiumhypochlorite. The molar ratios of components (a), (b) and (c) can varyadvantageously are about 1:1:1 with the molar ratio of component (a)relative to component (d) exceeding 1, e.g., about 5 to 10, in one literof deionized water. The active ingredient presumably reacts with thedecalcified, partially degraded collagen of the carious lesion resultingin a softening of the carious material. For information on this subject,reference is made to U.S. Pat. Nos. 3,886,266; 3,932,605; 3,991,107;4,012,842; and 3,776,825, the subject matter of which is incorporatedherein by reference. The aforesaid caries removal solution has arelatively short half life and should be prepared just prior to use.

A delivery system for administering the caries removal solution to thecarious lesion is disclosed in U.S. Pat. Nos. 3,776,825 and 3,943,628and can consist of a reservoir for the solution, a pump having an inletconnected to the reservoir and a handpiece with a uniquely designedapplicator tip connected to the outlet side of the pump. The solution isdelivered in a fine pulsing stream through the handpiece to the carioussite where it softens the decayed material. The dentist can then removethe softened carious material by light abrasion with the applicator tipwhile flushing with the solution.

Prior attempts to employ a caries removal device or system whichcomprises solely an applicator, a source or reservoir of the chemicalsolution and pump means connected between the applicator and thechemical solution source for periodically delivering the chemicalsolution under pressure to the applicator have not proven particularlysuccessful.

Desirably, the temperature of the caries removal solution at the time ofapplication to the carious lesion should be maintained within a rangethat affords maximum comfort to the dental patient, e.g., from about 90°F. to about 105° F., which covers the range of normal body temperatureof the patient. A temperature significant beyond this range can causediscomfort and may traumatize the patient.

The chemical solution is desirably applied to the carious lesion as asoothing, pulsating stream through a tube connected to the applicatortip at an optimum flow rate of about 35±5 ml/minute. The pulsationfrequency of the stream is desirably maintained in the range of about1000 to 1600 cycles/minute while its pressure is advantageously variedfrom about 10 to about 15 psi (per pulsation cycle). The flow rate,pulsation rate and pressure of the stream should be selected so as tobalance facility of application of the stream to the caries site withdue regard for the patient's comfort.

In order to achieve these objectives, the chemical solution must beheated from an ambient state when placed in the reservoir toapproximately 98.6°F., or normal body temperature. Thus, it has beensuggested in U.S. Pat. Nos. 3,863,628 and 4,012,842 to employ a heateras a part of the pump to bring the chemical solution to body temperatureas it is pumped to the applicator. The heater includes a heating elementembedded in a conductive block forming one side wall of the pumpchamber. The block is disposed opposite to, and spaced from, a flexiblediaphragm which is reciprocated so that chemical solution from areservoir is received in the chamber between the diaphragm and heaterblock and forced by the diaphragm out of the chamber to a hand-heldapplicator during reciprocation of the diaphragm by a cam mechanismconnected to a drive motor. This arrangement proves impractical in thatthe diaphragm cannot withstand the required frequency of operation cycleand fails after a relatively brief period of service.

Further, while the dwell time of the cam mechanism between the diaphragmand drive motor can be adjusted to increase or decrease the relaxation,or inactive, period of the pump to cause a pulsating drive of thechemical solution, there are no means to regulate the flow rate orpressure of application of the chemical solution, which, if too high,can cause harm to the patient by tearing of gum tissue adjacent thetreated teeth.

Thus, the need for an improved chemical solution delivery system forapplying the solution to a tooth with carious lesion in a pressure andflow-controlled, properly heated state, is desirable.

It has long been known that reciprocating, piston-type pumps can be usedto deliver a pulsating stream or jet of water to teeth for oral hygienesuch as cleansing, massaging and stimulating gum tissue. Examples ofsuch pump constructions are shown in U.S. Pat. Nos. 3,227,158 and3,420,228, the former illustrating the pump forming the basis of thewell-known WATER-PIK system. Such pumps do not exhibit the objectionablewear characteristics typical of a bellows or flexed diaphragm-typeactive pump element and through the introduction of suitable valvingadjacent the inlet and outlet of the pump chamber, flow and pressurecontrol of the pumped fluid may be obtained.

The disadvantages associated with known types of heated liquid deliverysystems are not confined to the aforementioned diaphragm-type pumpingmechanisms. The heater devices which have been incorporated into thesesystems are inadequate to the task for reasons which are inherent intheir design.

In a known type of heater device, a liquid to be heated is circulatedabout, or otherwise brought into direct contact with, an electricallypowered insulated heating element with heat being transferred from theheating element to the liquid. The heater device is associated withsuitable control means for heating the liquid at or within a few degreesof a predetermined temperature. The device operates well when there is asufficient flow of liquid past the heating element to continuously carryaway heat therefrom. However, when the delivery of electrical power tothe heating element is temporarily interrupted, e.g., when the flow ofliquid is discontinued, residual heat from the heating element continuesto transfer to the liquid in the vicinity of the heating element causingthe liquid to overheat. In fact, overheating can occur to such an extentthat the liquid in proximity to the heating element begins to boil. Sucha heater device is therefore entirely unacceptable for heating liquidsto be contacted with, or introduced into, the body. Such a device posesthe additional disadvantage that in the case of a corrosive liquid,there is a danger that the liquid will eventually penetrate the casingof the heating element thereby coming into electrical contact with theliquid. The hazard of an accidental electrocution in such circumstancesis in itself sufficient reason to preclude the use of such a heaterdevice in apparatus intended to supply a heated body-treating liquid.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a heated liquid deliverysystem having an improved pump device.

It is a further object of the invention to provide a heated liquiddelivery system having an improved liquid heating device, with orwithout combination with the aforementioned improved pump device.

It is a particular object of the invention to provide an improvedapparatus for intermittently supplying a dental treating solution to theoral cavity of a patient with the solution being heated to about thenormal body temperature of the patient.

In keeping with the foregoing objects there is provided a heated liquiddelivery apparatus comprising:

(a) a pump for delivering liquid to a heater device, said pumpcomprising a reciprocating piston-type pump; and

(b) an electrically powered, intermittently operated heater device forheating the liquid discharged from said pump to a predeterminedtemperature.

Further in keeping with the present invention, there is provided aheated liquid delivery apparatus comprising:

(a) a pump for delivering liquid to a heater device; and,

(b) an electrically powered, intermittently operated heater device forheating the liquid discharged from the pump to a predeterminedtemperature, said heater device comprising:

(i) a heat sink;

(ii) an electrical resistance heating element embedded within the heatsink such that when electrical power is delivered to the heatingelement, heat is transferred therefrom to the heat sink and when thedelivery of electrical power to the heating element is temporarilyinterrupted, residual heat in the heating element is transferredtherefrom to the heat sink, the total quantity of heat transferred tothe heat from the heating element not exceeding the heat capacity of theheat sink so that the temperature of the heat sink remains relativelyconstant both when electrical power is being delivered to the heatingelement and when the delivery of electrical power to the heating elementis temporarily interrupted; and,

(iii) a conduit for the flow of a liquid to be heated to a predeterminedtemperature substantially corresponding to the temperature of the heatsink, the conduit having an inlet for admitting liquid at a temperaturebelow the predetermined temperature and an outlet for discharging liquidat the predetermined temperature, the conduit being embedded within theheat sink such that heat is transferred from the heat sink to liquidpresent in the conduit raising the temperature of the liquid from thetemperature at the conduit inlet to the predetermined temperature at theconduit outlet.

In a preferred embodiment of the heating liquid delivery system of thisinvention, both the improved pump and improved heater device arecombined in the same unit with the unit benefiting from the advantagesof both components.

The reciprocating piston-type pump has been found to withstand therigors of the type of service to which the liquid delivery system is aptto be put, in particular, the dental treating procedures hereinaftermore fully described. Unlike the diaphragm or bellows-type pumps of theknown devices, a reciprocating piston-type pump is capable of providingfairly maintenance-free service for several hundred hours of operationcompared to perhaps 40 hours or even less for the former type pumpmechanisms.

The heater device of this invention completely overcomes thedisadvantages associated with the known type of heater device describedabove. Thus, the ability of the heat sink component of the heater deviceherein to continue to absorb residual heat from the heating element whenthe delivery of power to the heating element has been temporarilyinterrupted prevents the temperature of the heat sink from exceeding therange of temperature to which it is desired to heat the liquid presentin the conduit by any significant extent. In addition, since there is nodirect contact of the heating element with the conduit in the device ofthis invention, there is little, if any, opportunity for the liquidpresent in the conduit to even come into electrical contact with theheating element.

BRIEF DESCRIPTION OF THE DRAWINGS

Further objects and advantages of the invention will become apparentfrom the following description and claims, and from the accompanyingdrawings, wherein:

FIG. 1 is a perspective view of one embodiment of an apparatus inaccordance with this invention especially adapted for supplying a heatedcaries/plaque removal solution to the oral cavity of a patientundergoing treatment;

FIG. 2 is an exploded perspective view of the apparatus of FIG. 1;

FIG. 3 is a cross-sectional view taken substantially along the planeindicated by line 4--4 of FIG. 1;

FIG. 4 is an enlarged cross-sectional view of the check valve portion ofthe apparatus of FIG. 3;

FIG. 5 is a top plan view of the pump assembly of the apparatus of FIGS.1 and 2, with a portion broken away and illustrated in section forpurposes of clarity in describing the operation thereof;

FIG. 6 is a cross-sectional view taken substantially along the planeindicated by line 7--7 of FIG. 5 illustrating the flow and pressureregulator of the pump assembly;

FIG. 7 is a front view in elevation of one embodiment of a heater devicefor installation in a liquid delivery apparatus in accordance with thepresent invention;

FIG. 8 is a top plan view of the heater device of FIG. 7;

FIG. 9 is a side view in elevation of the heater device of FIG. 8 asseen from the right hand side of FIG. 8;

FIG. 10 is a graph illustrating the heating characteristics of theheater device of the present invention after flow of liquid at ambienttemperature has been commenced;

FIG. 11 is a graph illustrating the heating characteristics of theheater device of the present invention after flow of liquid has beeninterrupted;

FIG. 12 is a perspective view of the applicator of the apparatus of FIG.1 with the top portion thereof enlarged in the circled portion of theFigure to illustrate the details thereof; and,

FIG. 13 is a diagrammatic block diagram illustrating the overall processof using the heated liquid delivery apparatus of FIGS. 1-12 to deliver acaries/plaque removal solution for treatment of teeth.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings in detail, wherein like numerals indicatelike elements throughout the several views, FIGS. 1 and 2 illustrate theoverall assembly of an apparatus 50 the components and use of which arediagrammatically illustrated in FIG. 13. A two-piece case 52 consistingof a box 54 and cover element 56 is adapted to house motor 28, areciprocating piston-type pump 24, heater device 32 and fan 30 used tocool the motor. Suitable circuitry of known and conventional design ishoused at 58 to effect a variety of control functions such as regulatingthe operation of electric motor 28 and controlling the intermittentdelivery and interruption of power to heater device 32. Timer element 40is also mounted beneath cover element 56 and is connected via suitablecircuitry at 58 to visual indicator lamp 44 on cover element 56 whichwill be illuminated in a flashing or interrupted pattern after a givenpredetermined time interval once a reservoir 20 containing a quantity ofa caries removal liquid, designated Solution S, is seated on the coverelement 56.

In addition to a general power on/off switch (not shown), ahand-operated control 59 (FIG. 13) or, alternatively, a foot pedal 60,can be provided to intermittently activate the motor and pump assembly,and therefore, regulate the flow of Solution S as required. In eitherevent, a suitable visual display 62 can be provided to indicate whenpower to the entire unit is on and a second visual display 64 can beprovided to indicate when the hand-operated control or foot pedal hasactivated the motor/pump assembly.

An isolation transformer 65 can also be placed in the circuit betweenthe power source and the various electrical components of apparatus 50to preclude electrical shock to anyone touching case 52.

The source of caries removal Solution S can be maintained in twoseparate reservoirs and admixed just prior to application. Measuredamounts of particular components of the solution, as discussedheretofore, can be withdrawn from the two reservoirs, mixed in a smallmixing chamber to form the active caries removal solution and withdrawnfrom one reservoir, such as reservoir 20 shown herein, through a checkvalve and pumped through a heater and thereafter applied to the carioussite in fine pulsating stream through applicator 34. A suitableformulation for Solution S is as follows:

    ______________________________________                                        DL-2-aminobutyric acid                                                                           0.04-0.06 Mol                                              and/or Glycine                                                                Sodium Hydroxide   0.04-0.06 Mol                                              Sodium Chloride    0.04-0.06 Mol                                              Sodium Hypochlorite                                                                              0.005-0.01 Mol                                             Deionized Water    An amount sufficient                                                          to make one liter of                                                          solution                                                   pH of solution     approx. 10-12 at 20° C.                             ______________________________________                                    

As illustrated in FIGS. 2 to 4, inclusive, the bottom wall 66 ofreservoir 20 is provided with a pop-up check valve generally designatedby the numeral 22. The valve 22 includes a substantially planar disk 68adapted for mating seated engagement on an annular shoulder 70 of adepression 72 formed in bottom wall 66 of reservoir 20. A plurality ofspring fingers 74 extend downwardly from the bottom surface of disk 68and are adapted to snap over an annular shoulder 76 of a flared portionof a bore 78 on the interior surface of a downwardly extendingcylindrical extension 80 of bottom wall 66 of reservoir 20.

The exterior surface of cylindrical extension 80 is received in afitting 82 having an exterior threaded portion 84 adapted to receive nut86 to clamp the fitting 82 in an annular countersunk bore 88 in cover52. Extension 80 is received within central bore 90 of fitting 82 whenthe reservoir 20 is mounted on cover 52 and an annular O-ring seal 92 onthe exterior of cylindrical extension 80 forms a fluid imperviousconnection between the fitting 82 and cylindrical extension 80.

When the cylindrical extension 80 (as shown in FIG. 3) on the bottomwall 66 of reservoir 20 is inserted in the bore 90 of fitting 82 afterthe reservoir has been filled with caries removal solution, a downwardlydepending central stem 94 on disk 70 strikes an upwardly extendingcentral stem 96 in bore 90 of fitting 82 to cause the disk 68 to beraised relative to annular shoulder or seat 72. Spring retaining fingers74 exert sufficient force against annular shoulder 76 so as to retaindisk 70 of check valve 22 in bore 78 albeit raised from shoulder 72.

In the raised position of disk 70, Solution S can be drained fromreservoir 20 between disk 70 and annular shoulder 72 into bore 78, bore90 of fitting 82, and out through a series of openings 98 provided in acircular wall in the bottom of conduit fitting 82 into the bore 100 of acylindrical drain conduit 102 integral with the bottom of fitting 82.Solution S flows from drain conduit 102 through the inlet of pump 24 aswill be made clear hereinafter.

Simultaneously with the insertion of cylindrical extension 80 into bore90 of fitting 82, a second, downwardly extending cylindrical member 104on the bottom wall 66 of reservoir 20 having a permanent magnet 106fixed within the interior thereof is received within a depression 108 oncase cover 56. Mounted directly beneath depression 108 is timer 40 whichsenses the presence of magnet 106 to generate a current through thewell-known "Hall effect" to activate the timer delay circuitry whichultimately results in a visual display at lamp 44 after a predeterminedtime interval to signal that the potency of Solution S has becomeimpaired. At this time, reservoir 20 can be removed from its seat 110 indepression 112 on case cover 56 to change and/or replenish the reservoirwith a fresh quantity of Solution S.

Upon removal of reservoir 20 and extension 80 from fitting bore 90, theweight of the remaining Solution S in reservoir 20 will cause disk 68 toslide downwardly to seat against annular shoulder 72 or, if thereservoir is empty, finger pressure may be used to slide the diskdownwardly to reseat it on shoulder 72. Spring fingers 74 snap overannular shoulder 76 to maintain check valve 22 closed until reservoir 20is again filled and reseated on cover 56.

Drain conduit 102 of fitting 82 is received in an L-shaped elbow 114having an interior conduit 116 for connecting the bore 100 of drainconduit 102 with the inlet port 118 of a reciprocating piston-type pumpgenerally designated by numeral 24 and illustrated in detail in FIGS. 5and 6.

Pump 24 includes a housing 120 having an inlet port 118 leading to aninterior fluid receiving chamber 122, an outlet port 124 and a cylinderextension 126 receiving the plunger 128 of a reciprocable piston 130opposite to, but adjacent, outlet port 124.

Piston 130 is secured to an eccentrically mounted cam 132 fixed to ashaft 134 extending upwardly from the center of a rotatable gear 136 inmesh with a pinion 138 connected to output drive shaft 140 of electricmotor 28. Upon activation of motor 28, pinion 138 will rotate gear 136and shaft 134. Rotation of shaft 134 will cause eccentric cam 132 totravel about shaft 134 causing piston 130 to reciprocate in cylinderextension 126. Reciprocation of piston 130 in cylinder extension 126will cause plunger 128 to force fluid in chamber 122 out outlet port 124through tubing 142 to heater device 32.

The flow and pressure of liquid or Solution S exiting outlet 124 of pump24 can be regulated by flow and pressure regulator 26. This flow andpressure regulator includes a rotatable hollow valve body 144 threadedlyreceived at 146 in the interior of housing 120. The end of valve body144 within housing 120 includes a plurality of baffles 148 separated byopenings 150 through which Solution S can flow from inlet port 118 intothe hollow interior of valve body 144. Solution S can exit from theinterior of valve body 144 through a cylindrical bore 152 into theinterior of fluid receiving chamber 122 opposite piston plunger 128adjacent outlet port 124 of pump 24. Seated in the end of bore 152 isthe conical head 154 of a pressure valve 156. Valve 146 has a stem 158received in the wall of housing 120 opposite bore 152 in valve body 144.A coil spring 160 is compressed about stem 158 between housing 120 andhead 154 and exerts pressure on head 154 to seat the same in the end ofcylindrical bore 152. By threading or unthreading valve body 144relative to the threads 146 in the interior wall of housing 120, thepressure exerted by spring 158 on conical valve head 154 can be variedto either restrict or enlarge the size of the opening between bore 152and head 154 and thus the flow of Solution S out of valve body 144 aboutvalve head 154 into chamber 122 during the intake stroke of pump 24.

In operation, upon withdrawal of plunger 128 from cylindrical extension126, Solution S will enter chamber 122 from valve body 144 against thepressure exerted by valve head 158 against the flow of Solution Sthrough bore 152. By rotating valve body 144, the volume of Solution Sper reciprocable stroke of piston 130 entering chamber 122 can be varieddue to the relative seating of valve head 158 in bore 152 or thepressure exerted by head 158 against the flow intake of Solution S. Uponthe return of plunger 128 in cylindrical extension 126 to complete thepump cycle, the volume of Solution S conveyed into the chamber 122during the initial phase of the pump cycle is pushed out of chamberoutlet port 124, while the flow in chamber 122 maintains sufficientpressure on valve head 158 to maintain the end of bore 152 closed. Thevolume of flow of Solution S emanating through port 124 per reciprocablestroke of piston 130 also determines the maximum pressure of delivery ofSolution S. In this manner, a pulsating jet or stream of Solution S(i.e., on the last half, or return, of the pump cycle) at a controlledflow rate and pressure is delivered through outlet port 124.

Elbow 114 fits over, and can rotate or pivot on, an upright cylindricalextension 162 of housing 120 as shown by the arrows in FIGS. 2 and 5 sothat conduit 116 can be aligned with drain conduit 102 in the event ofimprecise manufacturing tolerances between cover 52 and box 54 of case56, or imprecise positioning of the components in container 54. A wireclip 166 (FIG. 2) can be used to aid in holding or clamping elbow 114 tohousing extension 162 and an O-ring seal 164 assures a fluid tight jointbetween the elbow 114 and housing 120.

A quantity of Solution S is delivered through flexible tubing 142 at acontrolled rate and pressure to inlet 177 of heating device 32illustrated in FIGS. 7 to 9. In the embodiment of heater device 32shown, a conduit comprising a coiled tube, e.g., of stainless steel, isprovided surrounding a conventional U-shaped insulated electricalresistance heating element embedded in a heat sink, e.g., a mass ofmetal advantageously having a high heat capacity. Materials useful forfabricating the heat sink include metals and metal alloys such asaluminum, copper, brass, iron, steel, etc., and non-metals, e.g.,various eutectic salt mixtures known in the art. Aluminum serves verywell as a heat sink since its high heat capacity endows it with theability to maintain a relatively constant temperature, e.g., within5°-10° F. of a predetermined level, depending, of course, on the mass ofthe metal and the power (thermal) output of the heating element.Aluminum is fairly low in cost and can be readily cast into just aboutany desired configuration with the heating element and conduit embeddedtherein.

The liquid to be heated is pumped through the conduit and electricalpower is applied to the heating element which transfers its heat to theheat sink. Heat is then transferred from the heat sink to the liquidraising its temperature to a predetermined extent. Such design andoperational factors as the heat capacity and mass of the heat sink, theresidence time of liquid in the conduit (itself influenced by suchfactors as fluid pressure and conduit length and diameter), theconfiguration of the heating element and the power level at which theheating element is operated will determine the temperature to which theliquid is heated. Those skilled in the art can readily establishsuitable design parameters for a given service requirement.

A temperature sensor means, e.g., a thermistor, associated with meansfor controlling the intermittent delivery and interruption of electricalpower to the heating element can be secured to the heat sink, preferablynear the conduit outlet. The temperature sensor continuously monitorsthe temperature of the heat sink and, in cooperation with theaforementioned power delivery control means, prevents the temperature ofthe heat sink from exceeding a predetermined level. This arrangement hasseveral advantages. During steady state operation, i.e., when liquid isflowing through the conduit, the temperature of the liquid at theconduit outlet tends to track the temperature of the heat sink in thevicinity thereof. The temperature sensor emits a control signal which isfed into, and processed by, an electronic circuit of known orconventional design housed at 58 (FIG. 2) which regulates the deliveryof power to the heating element. While liquid is flowing, thetemperature sensor primarily detects the temperature of the liquid atthe outlet. If the liquid flow within the conduit is interrupted, thetemperature of the heat sink in the vicinity of the temperature sensorwill start to rise because heat is no longer being removed from the heatsink by liquid flowing therethrough. The electronic power controlcircuit will respond to this increase in temperature by interruptingdelivery of power to the heating element if the temperature reaches apredetermined maximum level, e.g., on the order of 105° F. where theliquid being heated is to come into contact with a body. However, thetemperature of the stagnant liquid within the conduit will rise by onlya modest extent, e.g., approximately 3°-5° F. above the preferredtemperature range of about 90°-105° F. Eventually, the temperature ofthe heat sink, and with it the temperature of the liquid, will begin todrop because of thermal losses. When this occurs, the temperature sensorwill signal the power control circuit to resume delivery of electricalpower to the heating element. In operation, then, the ability of theheat sink to withstand large fluctuations in temperature permitsmaintenance of a predetermined temperature level within relativelyconstant limits, e.g., within 5°-10° F. as may be desired.

When the heater device has not been in operation for a relatively longperiod of time, the heat sink and any liquid present in the conduit willeventually attain ambient temperature. When the main power switch of theunit is turned on, full heating power is delivered to the heatingelement to elevate the temperature of the liquid. Placement of thetemperature sensor at the outer periphery of the heat sink permits thetemperature of the heat sink to rise, e.g., to approximately 105° F.,before the power is interrupted by the electronic power controller inresponse to a signal from the temperature sensor. This elevatedtemperature persists for a short period, e.g., for approximately fiveminutes, until thermal losses begin to lower the temperature back to thepredetermined level of, say, 98° F.

Referring to FIGS. 7-9, heat sink 176 of heater device 32 is provided asa casting of aluminum metal. Cast block 176 is provided with dependingrectangular support legs 181 and 182 for supporting the block on aplanar surface. A generally U-shaped electrical resistance heatingelement 170, e.g., of nichrome wire, and of suitable power rating, e.g.,from about 40 to about 120 watts and preferably from about 30 to about100 watts, surrounded by ceramic electrical insulation 170(a) andencased in a protective sheath 170(b), e.g., of stainless steel, isembedded in the aluminum casting and is provided with external leads 172and 174 for connecting the heating element to an electrical currentsource. Heating element 170 can be operated at a constant or varyingpower level. In the case of the latter, the heating element can beoperated for a brief period at the upper end of its rated power rangewhen the unit is first turned on in order to accelerate the heating ofcast block 176 and thereafter the power can be reduced to a lower level.A flow of Solution S is introduced into helical, or coiled, conduit 168at inlet 177 and, heated to the predetermined temperature, is dischargedfrom the conduit at outlet 178. Any suitable means, e.g., a pump, andpreferably reciprocating piston-type pump 24, can be used to supply aflow of liquid through conduit 168. Like heating element 170, conduit168 is embedded in the aluminum casting and is advantageously separatedfrom the heating element by a distance which is sufficient to prevent orminimize the possibility of hot spots developing in Solution S. Inoperation, heating element 170 will transfer heat to aluminum block 176which in turn will transfer heat to Solution S present in conduit 168.The temperature of the aluminum block governs the temperature ofSolution S, the two being approximately the same.

A temperature sensor 179, e.g., a thermistor, can be mounted on thesurface of aluminum block 176 near conduit outlet 178 as part of anarrangement for controlling the intermittent delivery and interruptionof electrical power to the heating element whereby the desiredpredetermined level of temperature is substantially maintained.

In order to maintain Solution S at an optimum temperature, e.g., on theorder of about 90° F. to about 105° F., the exterior dimensions of castaluminum block 176 and the length and diameter of coiled conduit 168 fora given flow rate of Solution S should be suitably selected. If block176 is too small, it will not possess a sufficient reserve of heatstorage capacity to be useful. The maximum amount of heat stored in theblock should not exceed its heat capacity for otherwise it will increasein temperature beyond the optimum level desired. If block 168 is toolarge, it will take too long to heat up to the desired temperature levelto be practical. In a preferred embodiment, it has been determined thatstainless steel tubing having a minimum length of approximately 48inches, a minimum internal diameter of about 0.125 inches and wallthickness of approximately 0.02 inches, embedded in an aluminum blockwhose approximate dimensions are 5 inches×2 inches×2 inches, issufficient in order to obtain and consistently maintain a predeterminedtemperature of about 90° F. to about 105° F. in Solution S at a flowrate of 35±5 ml./min. An optimum relationship has been found to existbetween the volume of the block/volume of Solution S at a flow rate of35±5 ml/min once the block has been heated to body temperature in orderto attain and maintain proper heating of the solution as it passesthrough heater device 32. Practical considerations involving economics,time delays in heating and reheating the liquid during intermittentoperations, size of the heater, the electrical power input, constructionmaterials of choice, the predetermined temperatures of choice, and thelike, will place realistic limits on the dimensions of the componentscomprising the heater device. Optimization is readily achieved by thoseskilled in the art.

The flow of Solution S may be interrupted from time to time. However, incertain applications, e.g., in the treatment of teeth with Solution S,since teeth are extremely sensitive to variations in temperature, thesolution should still be delivered at a relatively constant temperatureregardless of the frequency and duration with which the dentistinterrupts the flow of the solution. In the steady state, a continuousinput power of approximately 40 watts is usually required to heatSolution S from ambient temperature to a body temperature ofapproximately 98.6° F. A significant temperature gradient must existbetween heating element 170 itself and Solution S passing through heaterdevice 32 in order for sufficient heat energy to be transferred to thesolution. At steady state operation, when the solution is beingcontinuously passed through the heater device, electronic controls canregulate the power to the heating element as previously described sothat the solution will be discharged at the required temperature. Whenthe dentist releases a switch, e.g., a foot pedal 60 (FIG. 1) or othersuitable mechanism, Solution S ceases to flow through the heater.Residual heat energy stored in heating element 170 continues to transferto casting 176 causing the temperature of the casting, and therefore thesolution, to rise only a few degrees above the predetermined temperatureof 92°-105° F.

The relationship between the heat capacity of heating element 170 andthe heat capacity of aluminum casting 176 which thermally couplesconduit 168 containing Solution S to heating element 170, and the heatcapacity of Solution S contained in heater device 32 at any given timecan be empirically determined. The heater design exploits thisrelationship to limit the temperature rise during intermittent flowpatterns. This ensures both the safety and comfort of the patient. Theheat capacity of heating element 170 is limited to a small fraction ofthe heat capacity of the combined aluminum block 176 andliquid-containing stainless steel conduit 168. This limits the amount ofresidual heat energy which can transfer to the aluminum casting by theheating element after delivery of electrical power to the latter isinterrupted. In a preferred embodiment, the heat capacity of heatingelement 170 is from about 2 to about 10% of the heat capacity of theremainder of the heater; about 3 to about 5% is highly preferred.

A second temperature sensor 38 is provided as a safety device to preventthe temperature of the aluminum casting from exceeding a predeterminedlimit should temperature sensor 179 and/or its associated power controlcircuitry fail to operate properly.

As shown in FIG. 10, a typical time/temperature response curve is givenfor the heater device of FIGS. 7 to 9 where the temperature of SolutionS introduced at the conduit inlet is about 70° F. Within about twominutes of start-up employing a heating element output of about 40watts, there is a brief temperature overshoot which is advantageous inwarming the tubing and handpiece of a complete liquid delivery unit usedin the treatment of caries as shown in FIG. 12. Within six minutes or soof start-up, the temperature falls back to the predetermined level of98° F. As shown in FIG. 11, during steady pumping of Solution S, thetemperature of the device is uniformly maintained at about 98° F. Whenthe delivery of power to the heating element is temporarily interrupted,there is a modest increase in the temperature of stagnant Solution Spresent in the conduit (due to the residual heat in the heating elementtransferring to the aluminum block) which, however, is within anentirely safe level.

As shown in FIG. 12 illustrating applicator 34, flexible tubing 180 runsthrough the interior of a handpiece 182 having defined lands 184 foreasy qripping by a dentist. Tubing 180 is connected to a hollow steelscraping implement 186 having a spoon-shaped tip end 188. HeatedSolution S is pumped through tubing 180 into, and through, scrapingimplement 186 onto the caries/plaque site on tooth 36. Solution S willsoften the decay of the caries/plaque and it can then be removed byscraping with spoon-shaped end 188 of implement 186. As Solution S ispumped onto the site, the tip end 188 of implement 186 can also be usedto abrade the lesion to aid the solution S in softening the cariesmaterial and provide a fresh carious surface on which Solution S canact. Applicator 34 may be supported on a suitable bracket 190 mounted onone end of container 54.

As shown in FIG. 13 which diagrammatically illustrates the use of theforegoing apparatus in the treatment of caries, caries removal SolutionS in reservoir 20 is drained through a one-way check valve 22 into apiston-type reciprocating pump 24 provided with flow and pressureregulation means 26 at its inlet and outlet. The piston-typereciprocating pump 24 is driven by an electrical motor 28 which iscooled by a fan 30. Pump 24 causes the pulsating jet stream of SolutionS drained from reservoir 20 to flow through a heater device 32 into anapplicator device 34 provided with a scraping implement. The applicator34 directs the solution to the site of the caries at tooth 36.

Heater device 32 maintains the liquid jet stream at from about 90° F. toabout 105° F., or optimally at a temperature approximating normal bodytemperature, so that when it is applied to the site of the tooth caries,it will be neither too hot nor too cold and thus avoid discomfort to thepatient. The temperature of heater device 32 is sensed by a thermistor38 mounted on heater 32 which will cause a signal to be generated shouldthe temperature exceed a predetermined level to stop operation of motor28 and reciprocation of the piston of pump 24 until the solution coolsto approximately to the desired level at which time the motor will onceagain be started to cause the pump to pump the solution through theheater to the applicator.

Flow and pressure regulator means 26 used in the pump inlet and outletcauses the solution to flow at approximately 35 ml/min at a cyclepressure varying from 10 to 15 psi. This regulation of the flow of thesolution as it impinges in the mouth of the patient precludes gum tissuefrom being ruptured. Such flow and pressure regulation has been foundpractical via the utilization of a reciprocating piston-type pumpwherein suitable flow restrictions can be readily placed at the inletand outlet during the reciprocatory stroke of the piston to effect flowand pressure regulation.

The applicator causes the chemical solution to be discharged directly atthe caries site where it will aid in softening and turning the caries tothe extent it can be removed by hand manipulation of the scraperimplement associated with the end of applicator 34.

A timer element 40 can be activated upon opening of check valve 22 todrain reservoir 20, and a visual indication, after a given timeincrement, can be given by lamp 44 as the chemical solution has a veryshort half life, e.g., on the order of one hour. At that time, thesolution in reservoir 20 should be changed to a fresh solution.Operation of the delivery system may be initiated by closing of a manualhand operated switch 59 or a foot-operated pedal switch 60 which willcause operation of pump motor 28 from a pump power source 57. A lamp 62can indicate that power is on while a lamp 64 can be used to indicatethat the system is being operated by foot switch 60.

Heater device 32 is located adjacent to the applicator and scraper andseparate from the pump 24 so that: (1) heat loss to the ambientsurroundings is minimal after heating of the chemical solution and (2)heating of the chemical solution is independent of any active element inthe pump 24 so as to enable effective control of heat imparted to thesolution.

What is claimed is:
 1. Apparatus for delivering a heated liquid whichcomprises:a pump for delivering liquid to a heater device; and, anelectrically powered, intermittently operated heater device for heatingthe liquid discharged from the pump to a predetermined temperature, saidheater device comprising: a heat sink mass; an electrical resistanceheating element embedded within the heat sink mass such that whenelectrical power is delivered to the heating element, heat istransferred therefrom to the heat sink mass and when the delivery ofelectrical power to the heating element is temporarily interrupted,residual heat in the heating element is transferred therefrom to theheat sink mass, the total quantity of heat transferred to the heat sinkmass from the heating element not exceeding the heat capacity of theheat sink mass so that the temperature of the heat sink mass remainsrelatively constant both when electrical power is being delivered to theheating element and when the delivery of electrical power to the heatingelement is temporarily interrupted; and, a conduit for the flow of aliquid to be heated to a predetermined temperature substantiallycorresponding to the temperature of the heat sink mass, the conduithaving an inlet for admitting liquid at a temperature below thepredetermined temperature and an outlet for discharging liquid at thepredetermined temperature, the conduit being embedded within the heatsink mass separated a distance therein from the heating element and suchthat heat is transferred from the heat sink mass to liquid present inthe conduit raising the temperature of the liquid from the temperatureat the conduit inlet to the predetermined temperature at the conduitoutlet.
 2. The apparatus of claim 1 in whichthe heat sink mass comprisesa block of metal; the liquid flow conduit is corrosion-resistant and isembedded within the metal block in the form of a coil and separated suchdistance from the heating element as to prevent or minimize thepossibility of hot spots developing in the liquid, the apparatus furtherincluding means for regulating the intermittent delivery andinterruption of electrical power to the heating element in response tothe temperature of the metal block, said means including a thermistorpositioned proximate to the conduit outlet to continuously sense thetemperature of the metal block; and, means for discontinuing thedelivery of electrical power to the heating element to prevent thetemperature of the metal block from exceeding a predetermined levelshould said regulating means fail to do this.
 3. The apparatus of claim2 wherein said regulating means is operable to maintain a temperature ofliquid at the conduit discharge at or about the normal temperature of abody with which the liquid is to be contacted.
 4. The heater apparatusof claim 3 wherein the liquid is a caries/plaque removal solution forintroduction into the oral cavity.
 5. The apparatus of claim 1 in whichthe pump is a reciprocating piston-type pump, the apparatus furthercomprisinga reservoir for storing the liquid; check valve means betweenthe reservoir and the inlet of the pump for establishing communicationtherebetween when the reservoir is connected to the pump inlet; flow andpressure regulation means in the outlet of the pump for regulating theflow rate and pressure of the liquid delivered to the heater device;and, applicator means for delivering heated liquid from the heaterdevice for contact to a body or introduction into a body cavity.
 6. Theapparatus of claim 5 wherein said check valve means comprises:a pop-updisk seated flush in the bottom wall of the reservoir; and, meansconnected to the inlet of the pump for raising the disk to allow flow ofthe solution from the reservoir to the pump upon connecting thereservoir thereto.
 7. The apparatus of claim 5 wherein said flowregulation means further comprises:a hollow valve body disposed in thepump within the hollow interior thereof in communication with the pumpinlet, the valve body having an outlet port adjacent the pump outlet;and a spring-biased valve stem having an enlarged head normally closingthe outlet port of the hollow valve body; said valve body beingrotatably mounted on said pump such that by rotating same spring biaspressure between the valve stem and the valve body can be varied, tovary the pressure required to move the valve stem relative to the valvebody to open the valve body outlet port thereby correspondingly varyingthe flow rate of solution through the valve body.